This inventions relates to metal electrodes which are composed of an alloy of a basis-metal and an alloying element. In preparing such electrodes, a finely-divided or highly-porous basis-metal is employed such that the metal present in the electrode is in a finely-divided or highly porous state.
More particularly, the present invention relates to a process for preparing a metal electrode having electro-catalytic properties. To improve electro-catalytic properties existent in a basis-metal as defined hereinafter, or to obtain such electro-catalytic properties an alloying element is employed which imparts electro-catalytic properties to the basis-metal. In order to maximize current density per gram of electro-catalytic material, it is preferred that the material be present in a finely divided state or on a suitable carrier.
Electrodes of this type may be made by preparing a suitable metal alloy. Such preparation involves mixing a suitable metal alloy in the form of a powder with a powdery carrier material and, if necessary, in case a porous electrode is required, a pore-forming agent such as sodium sulphate. The whole mixture is then compressed at a high temperature to form an electrode, possibly with sintering. Finally, sodium sulphate, if present, is leached out with hot water. Such a method requires separate preparation of any alloy required, and, hence, is both cumbersome and expensive. Furthermore, compression at high temperatures may bring about substantial undesirable changes in the moistening properties of the electrode, which is particularly objectionable in the case of gas-diffusion electrodes.
Another drawback to such modes of preparation resides in the fact that it is difficult to prepare a series of electrodes having standard properties on a commercial scale.
According to the present invention, a process is provided whereby electrodes (or series of electrodes) differing in alloy constituents, but not in basis-metal, and having standardized properties, can be easily prepared.
A further object of the invention is to provide a means whereby initial basis-metal electrodes can be manufactured on a large scale and thereupon be modified by alloying, as required, and thereby eliminate the separate preparation of alloys.
Still another object of the present invention is to provide a process for preparing metal electrodes wherein the basis-metal is only slightly modified (i.e., a thickness of only up to a few atom layers), thereby providing electrodes having special electro-catalytic properties.